UI-V2 - Potential race condition loading plugins

[adkinsrs]

Occasionally I get the following error Uncaught (in promise) TypeError: Cannot set properties of null (setting 'innerHTML') in the following code block https://github.com/IGS/gEAR/blob/23832009af7b1ef1eb83a646d2c8535631cf603f/www/js/common.v2.js#L514-L522

This error happens spontaneously (cannot reproduce), and it seems the fetch is occurring before the element is created. I checked and the "fetch" is returning successfully but the plugin_name + "_html_c" element is not in the body. Maybe line 516 should be moved within the ".then" at line 520.

Two minor nitpicks/suggestions

1. Since plugin_html_element.id is already defined, use that in the getElementById instead of writing out the string again.
2. Replace var with let/const in the "for" loop (for consistency with modern JS)

[jorvis]

Addressed all these. There was definitely some un-refactored code copied here from v1 I didn't modernize.

[adkinsrs]

Still observing this (the second error was from clicking the "functional annotation dropdown".)